Concentration of phosphate-bearing material



Patented June 1 933 UNITED STATES PATENT orrics LAWRENCE H. LANGE, OE SALT LAKE CITY, UTAH, lASSIGNOR TO THE GENERAL, ENGINEERING COMPANY, 01 SALT LAKE CITY, UTAH, A CORPORATION OF UTAH CONCENTEATTON OF PHOSPHATE-BEARING MATERIAL No Drawing.

This invention relates to the concentration of phosphate-bearing material and has for its ob ect certain improvements in the method of concentrating phosphate-bearing material by 5 froth flotation. The invention relates more particularly to the froth flotation of phosphatic material associated with quartz gangue constituents. In the heretofore customary method of concentrating phosphate-bearing material by froth flotation, the phosphate-bearing part1- cles are floated while the gangue constituents are depressed. The concentration of phosphaterbearing material in this manner 1s 1-? rendered somewhat diflicult because the phosphate-bearin particles tend to partake of the nature 0% the gangue constituents. ,Although a substantial portion of the phosphate-bearing particles may be thus concentrated, there is a tendency .for gangue constituents to accompany the phosphate part1- cles into the froth layer maintained onthe surface of the body of pulp undergoing the froth flotation operation, as well as for phos phate-bearing particles to be de ressed together with the tailings.

As a result of my investigations, I have determined that phosphate-bearing material may be subjected to a froth flotation operation in which the gangue constituents are floated and the phosphate-bearing particles are depressed. Flotation v employed that alone or in combination with depress the phosstituents and selectively This up-sidephate-bearing particles.

I down step is particularly effective in sepa- 'aration of the phosphate-bearing particles furthermore phosphate-bearing gangue constituents t at go into reagents may be one another selectively float the gangue con- Application filed February 4, 1931. Serial No. 513,353.

from the gangue constituents is obtained when the slimes are first substantially removed. The presence of slimes in the pulp. is objectionable because the consumption of flotation reagents tends to increase.

In order to obtain a sharp separation of particles from gangue constituents, the material should be in a line state of subdivision. As far as my investigations thus far have gone, best results appear to be obtained when the flotation operation is conducted on material ranging in size from approximately 28 to 200 mesh.

Phosphate-bearing material of the fine state of subdivision contemplated necessarily includes a substantial amount of minute particles falling within the so-called slime range.

It is therefore better practice first to subject the phosphate-bearing material in the form of an aqueouspulp to a de-sliming operation. The slimes may be removed by a preliminary froth flotation treatment, tabling, classification or the like, before the addition of flotation-reagents adapted to float the gangue constituents. Thus, any suitable frothing agent of commerce may be employed; such as pine oil, coal tar derivatives, wood-oils, or any appropriate hydrocarbon and the like.

The de-slimed phosphate-bearing pulp is then suitably treated in order to efl'ect the froth flotation of gangue constituents and todepress phosphate-bearing particles. In order to inhibit the flotation of the phosphate-bearing particles, gangue constituents in a to flotation, a peculiar ployed.

Gangue constituents such as quartz are not readily floated in an acid circuit. It is therefore necessary to render themineral pulp properly alkaline. Lime (CaO) is highly useful for this purpose. In fact, it serves a triple function. While assisting in rendering the pulp highly alkaline, it also acts as a depressant to the phosphate-bearing particles; and as a collector for the gangue particles when used in conjunction with another appropriate reagent, such. as sodium oleate. we

while leaving the 35 a pressant reagents Other reagents, such as caustic soda, sodium carbonate and the like may also be employed to produce alkalinity; but their use appears to necessitate the employment of more dethan is needed when they are employed in conjunction with lime. These other alkaline reagents do not, moreover, appear to yield as marked a differential separation as with the use of lime.

In order to make the gangue constituents, such as quartz, floatable, suitable flotation reagents must be employed. Thus, compounds producing the oleate radical and metallic salts, such as lead nitrate, in solution, are highly effective. For example, a metallic soap such as sodium oleate in the form of red oil soap, acid mass sodium oleate, or ordinary soap are suitable. A soap compound called oleate on the market is particularly efficacious in the operation contemplated. Metallic salts such as ferrous sulphate, copper sulphate, zinc sulphate, aluminum sulphate, lead nitrate, copper nitrate, ferrous nitrate, and ferric nitrate or the like may be employed to assist in the flotation step. Alcoholic solutions (denatured alcohol or methanol) of the difierentsoaps and oleic acid are highly effective in causing quartz to float.

As stated above, the presence of lime in the pulp body not only assists in making the circuit alkaline, but it also tends to exert a depressant action on the phosphate-bearing particles. This depressant action is materially aided by the addition of a proper amount of a suitable carbohydrate, such as the well known starches.- Starch and lime in the mineral pulp not only tend to sink the phosphate-bearing particles, but they also assist in modif ing the gangue constituents so as'to make tl iem amenable to the floating ste Xlthough the soaps produce considerable froth, the froth does not generally have sufficient stability to support 1ts burden of gangue constituents. Additional frothing agent or agents should therefore be employed in conjunction with those particularly intended to depress the phosphate-bearing particles and to float the gangue constituents. Practically any of the conventional frothing agents may be employed, such as pine oil, coal tar derivatives, wood oils and the like. A coal tar derivative called tarol has been found to give unusually good results.

The flotation operation may be conducted in any suitable froth flotation gfparatus. Thus, the well known Callow or acIntosh cells may be employed. Finally disseminated air under pressure is released into the body of pulp at or near its bottom. As the air bubbles rise they tend selectively to be attached to the gangue constituents and lift them to the froth layer maintained on the surface.

The procedure for agitation of the pulp ed during the agitation period and flotation may be varied in certain respects. Thus, when employing the lime and starch, agitation should precede the flotation step. If tarol is used, it should be addin order to cause dispgrsion of the reagent throughout the pulp dy. If, on the other hand, pine oils are used, they may be added either before or after agitation of the pulp body. The point at which the frothing agent is added depends largely on its property of dispersion in aqueous solutions.

The metallic salts, such as, for exam le, copper sulphate, may be added either be ore or after agitation; but when added before agitation, the soap consumption is decreased. The soaps have no marked effect when added to the pulp during the agitation period. Hence, it is preferable to add the soap to the pulp in the flotation cell, where its desired action may at once be obtained.

If tarol is employed as a frothing agent, sodium oleate is the only reagent that needs to be added to the alkaline flotation circuit. Excellent results are obtained when employing this combination. To obtain the greatest efliciency and consequently to decrease excess consumption, it is advantageous to add the soap at intervals throughout the duration of the flotation step.

When employing lime and tarol, they are preferably added to the mineral pulp during the agitation period; i. e. prior to the actual flotation of the quartz constituents.

As a result of the agitation of the pulp in the presence of the lime and tarol, the slimes are substantially floated away. The oleate is then added, and the quartz particles are removed by froth flotation.

Extensive deposits of so-called hosphate rock are found in Florida. This phosphate-bearing material contains substantial amounts of quartz, sometimes referred to as silica sand. The material is found in nature for the most part in a finely subdivided state, many of the smallest particles falling within the so-called slime range. The phosphate is present generally as tricalcium phosphate. My invention as practiced on this material has shown very excellent results. To illustrate the practice of the present invention, the data submitted below may be considered in the examples set out.

The amounts of reagents specified are, as is conventional, computed on the basis of per ton of feed treated.

Example No. 1

In a test run on minus 28 to plus 48. mesh feed, the following procedure was followed :-the charge was given a five minute agitation (2 to 1 pulp density) with 15 pounds lime, pound. starch and No. 116 Yarmor pine oil. Flotation of the quartz was brought about with the addition of 3 pounds of acid mass sodium-oleate (in denatured alcohol solution), 0.8 pound of lead nitrate, and 0.5 pound Yarmor pine oil. The flotation pulp density was 7 to 1. 7

Percent B. P. L. (bone phosphate of lime) in concentrates= 15.2%.

Percent B. P. L. (bone phosphate of lime) in tailings= 66.0%.

Recovery of B. P. L. in tailings=7 7 Ewamp le N 0. Q

In a test run on minus 48 to plus 200 mesh feed, the following procedure was employed, producing a good grade of quartz concentrate with very small amounts present in the tailing :--an .average portion of the ore was agitated for a period of five minutes at 1 to 1 pulp density with 25 pounds lime, 2 pounds starch, 1 pound copper sulphate, and 2 pounds tarol. After agitation, the slimes produced therefrom were floated ofl, followed by the addition of 1.35 pounds of sodium oleate (red oil soap). Flotation was carried on at a pulp density of 3 to 1.

Percent B. P. L. in concentrates= 15.2%. Percent of B. P. L. in tailings =71.-83%. Recovery of B. P. L. in taihngs==70.%.

Emample N0. 3

In another test, an average portion of the ore was first de-slimedand then screened on a 48 mesh screen, the oversize particles being ground in a ball mill for 8 minutes; yielding a ground product conta ning 8% plus 48 mesh particles. The material is ground in order to reduce the size of the coarser particles of quartz to make them more I amenable to flotation. The ground product was then roughly de-slimed, and the deslimed product was added to the minus 48 mesh feed from the screening. This product was then given a 10 minute agitation (1 to 1 pulp density) with 25 pounds lime (GaO) per ton ofor'e and 3 pounds of tarol per ton of ore. After agitation, the slimes produced therefrom were floated ofl, followed by the addition of 1.0 pound oleate soap compound. The flotation operation was then carried out at a pulp density of 3 to l.

Percent Percent B. P. L. in slimes from grinding 63. 9 Percent B. P. L. in concentrates 12. 4 Percent B. P. L. in tailings 73-. 9 Recovery of B. P. L. in slimes 7. 3 Recovery of B. P. L. in tailings 65. 4

Total recovery of B. P. L 72. 7

The rise of the gangue particles and the fall of the phosphate-bearing particles appear to be due in large part to the manner in which the pulp is initially conditioned. As pointed out above, the pulp is suitably conditioned with the alkaline agent in advance of the flotation step itself. The-conditioning period, for example 30 minutes, with the lime appears to cause a wetting of the phosphate-bearingparticles, and thus renders them non-amenable to froth flotation when the collecting agent, such as soap, is ultimately added. The frothing agent, such as steam distilledpine oil, is advantageously presentin the pulp during the conditioning pei'iod, thus permitting a thorough dissemibearing. material, the step which comprises subjecting the material in the form of an alkaline pulp to a froth flotation operation nitrate solution adapted to ;float quartz gangue constituents.

3. In a method of concentratingphosphatebearing material, the step which comprises subjecting the material in the form of an alkaline pulp to a froth flotation operation in the presence of sodium oleate and lead nitrate adapted to float quartz gangue constituents and in the resence of an oil adapted to depress phosp ate-bearing particles.

4. In a method of concentrating phosphatebearing material by froth flotation, the step which comprises subjecting the phosphatebearing material in the form of an alkaline pulp to a conditioning period until the phosphate-bearing particles are I rendered non-amenable to froth flotation when a collecting agent is added to the pulpwhereby quartz gangue constituents may be selectively floated while the phosphate-bearing particles are depressed.

5. Method according to claim 4, in which lime is added to render the pulp alkaline and to depress phosphate-bearing particles.

6. Method according to claim 4, in which a suitable hydrocarbon is added to make a stable froth and to depress phosphate-bearing particles.

7. Method according to claim .4, in which a suitable oil is added to make a stable froth and to depress phosphate-bearing particles.

8. Method according to claim 4, in which a suitable coal-tar derivative is added to depress phosphate-bearing particles.

9. Method according to claim 4, in which lime and a suitable oil are added to render the pulp alkaline and to depress phosphatebearing particles.

10. Method according to claim 4, in which p in the presence of sodium olcate and lead lime and a suitable coal-tar derivative are added to render the pulp alkaline and to depress the phosphate-bearing particles.

11. Method according to clalm 4, in which a soap is added to float quartz gangue constituents.

12. Method according to claim 4, in which sodium oleate is added to float quartz 'gangue constituents.

13. Method according to claim 4, in which acid mass sodium oleate is added in alcoholic solution to float quartz gangue constituents.

14. Method according to claim 4, in which a metallic salt in solution is added to float quartz angue constituents. e

15. ethod according to claim 4, in which a soap and a metallic salt are added in solution to float quartz gangue constituents.

16. Method according to claim 4, in which lime, a soap and a suitable oil are added.

17. Method according to claim 4, in which lime, sodium oleate and a suitable oil are added.

18. Method according to claim 4, in which lime, a, soa and a suitable coal-tar derivative are ad ed. 7

19. Method according to claim 4, in which lime, a soap, a metallic salt in solution, and a frothing oil are added.

20. Method according to claim 4, in which the pulp of phosphate-bearing material is initially subjected to a slime removal operation.

21. Method according to claim 4, in which the conditioning period is effected in the sirlnultaneous presence of lime and a frothing o1 22. Method according to claim 4, in which the conditioning period is effected in the simultaneous presence of lime and a frothing oil, and then subjecting the pulp so treated to a froth flotation operation in the presence of soap.

In testimony whereof I aflix my signature- LAWRENCE H. LANGE. 

